Cu-NMR studies of Nd_2-xCe_xCuO_4-y

The zero field Cu-NMR of Nd_2-xCe_xCuO_40-y around 90-140 MHz indicates clearly that the antiferromagnetically ordered state is situated near the superconducting state in the electron doped cuprate. Three distinct components of the Cu-NMR signals appear for Ce-doping. The two kinds of zero-field NMR signals with large electric quadropole interactions are observed for 0.05≦x≦0.20, while the additional one with the anomalous absence of the electric field gradient at Cu sites is obtained for the Ce-concentrated region. The result suggests that the local electronic configuration at Cu sites changes significantly with Ce-doping. The temperature and Ce-concentration dependences of Knight shift, line width and nuclear relaxation time are also investigated.